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Rates of reaction of trapped electrons produced by pulse radiolysis in 9.5 mol dm-3 LiCl solutions have been measured for electron acceptors which show widely differing reactivities with trapped and dry electrons. In the glass at 138 K where tunnelling occurs the reaction rate reflects the ability of the acceptor to react with dry electrons rather than with trapped electrons. For those acceptors which do not react with dry electrons the reaction rate is much slower.At higher temperatures, where the glass is softer, the reaction rates correspond more closely to the reactivities of the acceptors with trapped electrons.

Reactions of et with several solutes have been investigated over a wide range of temperature in 50/50 v/v ethylene glycol+water (EG+HzO) and 10 mol dm-3 OH-aqueous solutions.In the fluid media the reactions are generally diffusion controlled, and values of the encounter radius, r, between et and solute have been estimated by applying the theory of time-dependent rate constants to the kinetics.In the rigid media the reaction rate of et with solutes is independent of temperature and proportional to log (time). The rate varies from one solute to another, and is faster in 10 mol dm-3 OHthan in EG+HzO. The kinetics are consistent with el tunnelling from trap to trap in the matrix and reacting with the solute when it becomes trapped within the encounter radius Y. Independent assessments of Y from tunnelling kinetics agree well with those obtained from diffusion kinetics.The eiry capture efficiency of each solute has been estimated from its effect on G(et). The efficiencies of H+, Cuz+ and Fe(CN),NOZare negligibly small, which is in marked contrast to their high reactivities with et.Evidence for long lived encounter pairs of ei and Hf, et and Cu2+, and el and SeOi-at low temperatures is presented.* The beginning of the pulse is taken as the zero of time.

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